Evil Dave is an aspiring "Evil Doer". He appears in Shadow of the Storm as a member of an evil cult trying to resurrect an ancient Demon. He is also a sub-quest in Recipe for Disaster in which you must free him by feeding him spicy stew that you have to make, by getting your cat to catch hell-rats that drop certain spice that you must add to the stew. He lives in his Mother's basement in Edgeville. He is possible to contact by using NPC contact after the Dream Mentor quest. However, he does not say anything important.
It was revealed that he came to be part of the Lumbridge Secret Council because it was decided that an evil wizard should be included, but it had to be one that was harmless (for the sake of everyone). Currently, Evil Dave is the only one who has those requirements.